1. Field of the Invention
The present invention relates to a reflector movable type headlamp for a vehicle in which a reflector having a light source attached thereto is tiltably supported on a lamp body by an aiming mechanism. More particularly, the invention relates to a reflector movable type headlamp for a vehicle having an aiming mechanism with structure such that a nut member used as an aiming point component is supported by a nut sliding guide formed in the lamp body.
2. Description of the Related Art
In a related art reflector movable type headlamp for a vehicle, a reflector formed of a synthetic resin having a light source attached integrally therewith is supported by an aiming mechanism. The aiming mechanism is constituted by one ball-and-socket joint to be a tilt fulcrum and two nut members to be moving fulcrums which can be screwed into two aiming screws and can advance and retreat in an axial direction respectively on the front side of a lamp body 1 formed of a synthetic resin as shown in FIG. 30.
More specifically, an aiming screw 4 is rotatably supported on a screw insertion hole 1a provided in the lamp body 1, and a nut member 5 formed of a synthetic resin, which is attached to a bracket 2a extended and formed in the reflector, 2 is screwed into a screw portion 4a of the aiming screw 4 extended forward from the lamp body 1. When the aiming screw 4 is rotated, the nut member 5 advances or retreats along the aiming screw 4 so that the reflector 2 is tilted around a tilt axis connecting the ball-and-socket joint and the nut member to be screwed into the other aiming screw. Consequently, the optical axis of the lamp can be regulated.
The aiming screw 4 is formed of metal and has a rear end with which a cap-shaped gear 7 is integrated, and the aiming screw 4 can be rotated by using a driver D. Moreover, the aiming screw 4 inserted into the screw insertion hole 1a from the rear part of the lamp body 1 is elastically supported in a longitudinal direction by a push-on-fix 8 formed of metal and is positioned and fixed.
Further, an O-ring 9 to be a seal member is provided in the screw insertion hole 1a rotatably supporting the aiming screw 4, in part for waterproofing purposes in the rotating support portion of the aiming screw 4.
In a headlamp comprising the aiming mechanism having such a structure, however, there is a possibility that a weight W of the reflector 2 might act on the tip portion of the aiming screw 4 cantilevered by the screw insertion hole 1a. As such, the aiming screw 4 might be rocked with respect to the screw insertion hole 1a to vibrate the reflector 2. Therefore, the aiming screw 4 is strongly pressed and held in the peripheral edge portion of the screw insertion hole 1a by means of the push-on-fix 8 formed of metal, thereby preventing the rocking motion of the aiming screw 4 (the vibration of the reflector 2).
However, there is a problem in that the rotating property of the aiming screw 4 is deteriorated which can make carrying out an aiming operation difficult if the force for holding the aiming screw 4 by the push-on-fix 8 is increased.
Therefore, the applicant has proposed JP-A-2000-165437 (filed in Jun. 2, 2000). As shown in FIG. 31, at the side of a nut member body 5 provided with a female screw portion to be screwed into the aiming screw 4, a nut member has such a structure that an engagement projection 6 to be an attachment portion to a bracket 2a on the reflector 2 side and a slider portion 7 to be a slide engagement portion with a sliding guide 8 provided in a lamp body 1 are integrally formed orthogonally as seen from the front, and the slider portion 7 is supported and carried by the sliding guide 8 so that a weight load on the reflector 2 side acting on the aiming screw 4 is relieved to suppress the rocking motion (vibration) of the reflector 2. The reference numeral 9 denotes a front lens, the symbol a denotes an aiming fulcrum, the symbol Lx denotes a horizontal tilt axis, and the symbol Ly denotes a vertical tilt axis.
In the related art (JP-A-2000-165437) described above, however, the weight load on the reflector 2 side is carried by the sliding guide 8. Therefore, while the weight load on the reflector 2 side does not act as a bending moment on the aiming screw 4, a torsional moment is generated on the nut member by an inertial weight on the reflector side acting on the engagement projection 6 which is offset and provided on the side of the nut member body 5 screwed into the aiming screw 4. As such, it may become difficult to reliably suppress the vibration of the reflector. Moreover, there has also been proposed a problem in that the nut member might be freely rotated with respect to the aiming screw so that proper aiming cannot be carried out when the torsional moment repetitively acts on the nut member as shown in the open arrows of FIG. 31.
In addition, there is also a problem in that the nut member takes a T-shape or an L-shape seen from the front and therefore can be bulky, resulting in an increase in the size of the lamp body.
In order to solve the various problems described above, therefore, the applicant has proposed JP-A-2000-400085 (tiled on Dec. 28, 2000). In this application, a nut member itself to be screwed into an aiming screw constitutes a ball portion 5a, and an engagement hole 2b constituting a ball receiving portion is formed on a bracket 2a on the reflector side as shown in FIG. 32.
In JP-A-2000-400085, however, the various problems can be solved and the ball receiving portion (engagement hole) 2b is provided on the bracket at the reflector side. For this reason, the structure of the bracket and that of a mold for reflector molding are complicated so that there is a new problem in that a manufacturing cost is increased correspondingly,